This invention relates to the generation of electronic representations of moving images and, more particularly, to an improved method and apparatus for creating animated images from stored image data elements with substantially reduced computational requirements.
The creation of high quality animated images is generally considered to be tedious and expensive. Before the advent of computer-generated animation, each animated film required artists to produce large numbers of drawings, with thousands of drawings being necessary to produce even a short film segment. In recent years, the development of sophisticated computer animation techniques permits artists' time to be more efficiently utilized, with the computer serving to automatically perform a number of tasks, including computation of objects as they are to appear in an image and generation of so-called "in between" frames of an animated sequence. However, computer-generated animation has only recently begun to approach the quality of non-automated manually created animation. However, as computer-generated animation is produced with higher quality and higher resolution, the number of computations necessary for generating images from stored image data elements grows quickly, and this tends to increase the necessary processor and memory capabilities and/or the time necessary for producing the animation. The result is a higher cost of producing computer-generated animation.
It has been previously demonstrated that the characteristics of human vision can be taken into account in the design of equipment for encoding and decoding video signals or storing video signals with reduced bandwidth requirements. For example, an electronic video signal can be encoded at reduced bandwidth by lowering the frame refresh rate of the high spatial frequency components, while maintaining the frame refresh rate of at least a portion of the low spatial frequency components at the standard rate. If done in a specified manner, this will not cause substantial degradation in the ultimately displayed image, since human vision cannot perceive changes in high spatial resolution information at as fast a rate as it can perceive changes in low spatial resolution information. Accordingly, an electronic video encoding and decoding system has been devised which takes advantage of this, and other characteristics of human vision by encoding higher spatial resolution video components to be at a temporal information rate which approximately corresponds to the highest rate actually perceived by the human vision system for such components; thereby eliminating the need to encode these components at a higher rate, which inherently wastes bandwidth. Also, it has been shown that the low spatial resolution information can be generated in a form which is compatible with standard television video, e.g. NTSC video. In this regard, reference can be made, for example, to U.S. Pat. Nos. 4,517,597, 4,628,344, 4,652,909, 4,667,226, and 4,701,783, all assigned to the same assignee as the present application.
The described techniques are very useful in processing video signals to reduce the bandwidth necessary for transmission and/or storage of the signals. It has been suggested that techniques which take advantage of the indicated characteristics of human vision could also be used advantageously in the creation of animated images. However, to Applicant's knowledge, practical techniques and systems for creating animation with substantial saving of computational complexity and/or storage requirements and/or time have not been forthcoming.
It is among the objects of the present invention to provide an improved and practical method and apparatus for creating electronic representations of animated images from stored image data elements with substantially reduced computational requirements.